Abnormal attitudes of the limb occur earlier, and are more pronounced in cases in which pain and other irritative symptoms of articular disease are well marked, and are best illustrated by the attitudes assumed in disease of the hip.  They are due to reflex or involuntary contraction of the muscles acting on the joint, with the object of placing it in the attitude of greatest ease; they also disappear under anaesthesia.  With the lapse of time they not only become exaggerated, but may become permanent from ankylosis or from contracture of the soft parts round the joint.

Startings at night are to be regarded as an indication that there is progressive disease involving the articular surfaces.

The formation of extra-articular abscess may take place early, or it may not occur till long after the disease has subsided.  The abscess may develop so insidiously that it does not attract attention until it has attained considerable size, especially when associated with disease of the spine, pelvis, or hip.  The position of the abscess in relation to different joints is fairly constant and is determined by the anatomical relationships of the capsule and synovial membrane to the surrounding tissues.  The bursae and tendon sheaths in the vicinity may influence the direction of spread of the abscess and the situation of resulting sinuses.  When the abscess is allowed to burst, or is opened and becomes infected with pyogenic bacteria, there is not only the risk of aggravation of the disease and persistent suppuration, but there is a greater liability to general tuberculosis.

The sinuses may be so tortuous that a probe cannot be passed to the primary focus of disease, and their course and disposition can only be demonstrated by injecting the sinuses with an emulsion of bismuth and taking X-ray photographs.

Tuberculous infection of the lymph glands of the limb is exceptional, but may follow upon infection of the skin around the orifice of a sinus.

A slight rise of temperature in the evening may be induced in quiescent joint lesions by injury or by movement of the joint under anaesthesia, or by the fatigue of a railway journey.  When sinuses have formed and become infected with pyogenic bacteria, there may be a diurnal variation in the temperature of the type known as hectic fever (Fig. 11).

Relative Frequency of Tuberculous Disease in Different Joints.—­Hospital statistics show that joints are affected in the following order of frequency:  Spine, knee, hip, ankle and tarsus, elbow, wrist, shoulder.  The hip and spine are most often affected in childhood and youth, the shoulder and wrist in adults; the knee, ankle, and elbow show little age preference.

Clinical Variations of Tuberculous Joint Disease.—­The above description applies to tuberculous joint disease in general; it must be modified to include special manifestations or varieties.